Joe Sato (Saitama University )

1. Joe Sato (Saitama University ) Measuring lepton flavor violation at LHC with a long-lived slepton in the coannihilation region Satoru Kaneko,Takashi Shimomura, Masato Yamanaka,OscarVives Collaborators Physical review D 78, 116013 (2008) arXiv:1002.????

2. 1, Introduction

3. 1, Introduction In Standard Model (SM) Lepton Flavour Violation (LFV) through the neutrino oscillation But … Forever invisible Detection of the LFV signal One of the evidence for beyond the SM

4. 1, Introduction One of the candidates for beyond the SM Supersymmetric (SUSY) model Supersymmetry Symmetry between boson and fermion Lepton Slepton Gauge bosonGaugino Why SUSY models ?? Stability of Higgs mass, dark matter, gauge coupling unification, hierarchy problem, and so on

5. 1, Introduction In Supersymmetric (SUSY) models Enhancement of LFV through the slepton mixing Detectable at future experiments Understanding the structure of slepton mixing Observational results of LFV search experiments Possible to confirm the SUSY model !

6. 1, Introduction Purpose in this work Understanding the structure of slepton mixing What is the key ingredient ? Long-lived stau Where is the stage ? Large Hadron Collider (LHC) experiment

7. 2, Long-lived stau

8. Setup in the work Framework Minimal Supersymmetric Standard Model (MSSM) Lightest supersymmetric particle (LSP) Lightest neutralino Dark matter ∴ R-parity Next Lightest Supersymmetric Particle (NLSP) Lighter stau

9. Coannihilation scenario [ K. Griest and D. SeckelPRD 43 (1991) ] At around the same time LSP DM and NLSP stau decouple from thermal bath Enough to reduce DM density Providing DM abundance consistent with WMAP Requirement for coannihilationscenario

10. Long-livedstau in the coannihilation scenario Attractive parameter region in coannihilation scenario dm ≡ NLSP mass － LSP mass < tau mass (1.77GeV) Can not decay into two body Phase space suppression Long lifetime

11. Long-livedstau Phys. Rev. D73:055009-1-8, 2006 Staulifetime (s) Without slepton mixing At the LHC, the long-lived stau would be produced Available for investigating the slepton mixing

12. Furthermore it can offer a solution to Lithium Problem in Standard Big-Bang Nucleosynthesis Phys.Rev.D76:125023,2007Phys.Rev.D78:055007,2008arXiv:1001.1217

13. 3, Slepton mixing as a source of LFV

14. With or without slepton mixing Without slepton mixing Impossible to decay into two body Long-lived and would escape from detector With slepton mixing Decay into two body opens ! ~ 2 Decay rate of stau ( Slepton mixing ) Measurements of the stau lifetime Strong sensitibity to slepton mixing parameter

15. Decay with slepton mixing Decay process with LFV Slepton mass matrix Slepton mixing parameter

16. Decay with slepton mixing Decay process with LFV Decay rate Effective coupling Slepton mixing parameter

17. Bounds on slepton mixing parameter Slepton mixing parameter Bounds on slepton mixing parameter ⋍ For stau mass 300GeV L. Calibbi, J. Jones-Perez, and O. Vives, Phys. Rev. D 78,075007 (2008). More strict constraint on mixing parameter !

18. Stau lifetime with LFV Staulifetime (s) With slepton mixing

19. Stau lifetime with LFV Staulifetime (s) With slepton mixing Stau decay into tau and neutralino Insensitive to slepton mixing parameter

20. Stau lifetime with LFV Staulifetime (s) With slepton mixing Competition between LFV decay and 3(4) body decay Very good sensitivity to small slepton mixing parameter

21. 4, LHC phenomenology

22. Looking for stau and that decay at the ATLAS One of the LHC detector ATLAS Production rate of SUSY particles ⋍ For stau mass 300GeV [ P.Z. Skands, Eur. Phys. J. C 23, 173 (2002) ] Produced number of stau

23. Expected number of stau decay at the ATLAS Decay probability Lorentz factor Expected number of decay In the following discussion

24. Constraint on slepton mixing parameter at ATLAS Expected number of LFV stau decay All of the staus decay before they reach detectors No signals of heavy charged particle

25. Constraint on slepton mixing parameter at ATLAS Expected number of LFV stau decay Staulifetime (s) All of the staus decay before they reach detectors No signals of heavy charged particle Lower bound on slepton mixing parameters

26. Constraint on slepton mixing parameter at ATLAS Expected number of LFV stau decay Staus decay inside detectors

27. Constraint on slepton mixing parameter at ATLAS Expected number of LFV stau decay Staulifetime (s) Staus decay inside detectors Slepton mixing parameters are strictly constrained

28. Constraint on slepton mixing parameter at ATLAS Expected number of LFV stau decay All of staus leave detectors Lower bound on stau lifetime

29. Constraint on slepton mixing parameter at ATLAS Expected number of LFV stau decay Staulifetime (s) All of staus leave detectors Stringent upper bounds on slepton mixing parameters For further study on LFV Let’s construct bigger detector !!

30. 5, Summary and discussion

31. Summary Slepton mass matrix includes off-diagonal elements, and it leads to Lepton Flavour Violation (LFV) Important to understand slepton mixing structure for study LFV In the MSSM coannihilation scenario, NLSP stau can be long-lived Stau lifetime is sensitive to the slepton mixing Stau lifetime > 10 (s) -12 Strict lower bound on slepton mixing parameter 10 (s) < lifetime < 10 (s) -10 -8 Stau lifetime > 10 (s) -5 Strict upper bound on slepton mixing parameter LHC provides a very good opportunity to study LFV !!

32. Discussion What is the source of slepton mixing ?? SUSY seesaw models with right-handed neutrinos Energy scale LFV source in the neutrino Yukawa matrix Renormalization Group Evolution (RGE) Energy scale Slepton mixing in slepton mass matrix Slepton mixing parameter

33. Discussion What is the source of slepton mixing ?? SUSY seesaw models with right-handed neutrinos Energy scale LFV source in the neutrino Yukawa matrix Renormalization Group Evolution (RGE) Energy scale Slepton mixing in slepton mass matrix For large mixing (MNS-like) An element of MNS matrix

34. Discussion What is the source of slepton mixing ?? SUSY seesaw models with right-handed neutrinos Energy scale LFV source in the neutrino Yukawa matrix Renormalization Group Evolution (RGE) Energy scale Slepton mixing in slepton mass matrix For small mixing (CKM-like)

35. Example in MSSM with RH neutrino

36. Appendix

37. Original thermal relic scenario On the stage of DM freeze-out Decouple species : DM only Pair annihilation rate of DM decides DM relic abundance Too week to reduce DM density sufficiently DM over abundance !!

38. Coannihilation scenario [ K. Griest and D. SeckelPRD 43 (1991) ] On the stage of DM freeze-out Decouple species : DM and NLSP Annihilation rates of DM and NLSP decide DM relic abundance Enough to reduce DM density Providing DM abundance consistent with WMAP

39. Requirement for coannihilation For the coannihilation process Two species decoupling at around the same time Ingredient of the decoupling point mass of decoupling particle Requirement for coannihilation mechanism

40. Total abundance of stau and neutralino